Devices that dispense active ingredients into the air, such as volatile actives, are used for many reasons, including dispensing fragrances, insecticides, deodorants, and many other types of chemicals (hereinafter, collectively referred to as “actives” or “active ingredients”) that are intended to have some desired effect when present in the ambient air of a space such as a room indoors or an outdoor space.
Some such dispensing devices are called passive dispensers in that the device does not include any apparatus that requires some form of energy, often electricity, to dispense the active. Passive dispensers often have some form of carrier, such as a gel or liquid, that has been impregnated or otherwise carries the active, and the carrier and active are contained within an enclosed container. When it is desired to dispense the active, the container is somehow opened, such as by removing an impermeable membrane covering an opening into the container, so that the carrier is in communication with the atmosphere surrounding the device, which thereby allows the active to volatilize from the carrier into the air and disperse passively into the surrounding atmosphere.
Other dispensing devices are called active dispensers in that the device includes an apparatus that requires some form of energy, such as electricity, to activate the apparatus so as to actively assist in dispensing the active into the surrounding atmosphere. Active dispensing devices include devices with heating elements for heating the carrier and devices with fans for blowing air across or from the carrier into the surrounding atmosphere. In general, the purpose of an active dispenser is to speed up the rate at which the active is dispersed into the surrounding atmosphere over passive dispensers so that the desired effect of the active is achieved in a shorter period of time from the time of initial activation of the dispensing device.
One particularly common form of carrier used in both passive and active dispensing devices is a gel, wherein one or more active ingredients, such as fragrance and/or insecticide, is mixed with at least one or more gellant agents in an aqueous solution while in a liquid phase and allowed to transition into a semi-solid gel phase at normal ranges of room temperature, such as generally between 50° F. (10° C.) and 100° F. (38° C.). When the gel is closed within an enclosed container, the gel and the active ingredient are maintained in a relatively stable form. When the container is opened to the surrounding atmosphere, the active ingredient(s) are able to volatilize into the surrounding atmosphere, and the water in the gel also slowly evaporates. At the end of the useful life of the dispenser, the volume of the gel is usually substantially diminished because of the evaporation of the water from the gel, and the active ingredients are substantially completely dispersed from the gel. Basic examples of such dispensing devices are disclosed, for example, in U.S. Pat. No. 2,949,710 to Wheeler, U.S. Pat. No. 6,171,560 to Pesu et al., and U.S. Patent Application Publication No. 2004/0094635 of Harris et al.
In many passive dispensers, the noticeable effect of the active ingredient has a high initial spike that subsequently quickly decreases with time to a much lower noticeable effect in a generally L-shaped curve. This rapid decrease in noticeable effect may be caused by many factors, including an actual decrease in the amount of active ingredient that is dispersed with time, i.e., rate of dispersal or diffusion. Another reason for the decrease in noticeable effect, especially dispensers that dispense fragrances, may be attributed to desensitization or habituation of a person's olfactory senses to the fragrance, which causes the person to notice the initial fragrance quite strongly, but over time, even if the level of fragrance remains constant, the person becomes habituated or desensitized to the fragrance such that the person does not seem to notice the fragrance as strongly as when the person was initially exposed to the fragrance.
The present disclosers have identified that it would be desirable to improve a dispensing device for a volatile active in such a manner that the noticeable effect of the active ingredient does not diminish as rapidly or at all over the useable life span of the dispensing device so that the noticeable effect remains more strongly noticeable in the surrounding atmosphere for a longer period of time.